This invention concerns a method, a portable electronic device, and an entertainment system in each of which power consumption can be economized by changing a CPU operation clock.
A conventional memory card device, etc. (slave machine) that is used with being inserted into an information device or other master machine such as an entertainment system represented by a game machine has an interface for connecting it to the main unit (master machine) of the information device and a nonvolatile memory element for storing data.
FIG. 1A shows an example of the composition of the key parts of such a conventional memory card device. The conventional memory card 10 has a control unit 11 for controlling its operation, a connector 12 for connecting the card device to a terminal provided in a slot of an information device, and a nonvolatile memory 16 for storing data. Connector 12 and nonvolatile memory 16 are connected by the control unit 11.
Control unit 11 may be, for example, a microprocessor (so labeled in the diagrams). Used as nonvolatile memory 16 is, for example, a flash memory such as an EEPROM (electrically erasable and programmable ROM). A microprocessor is also sometimes used for the connection interface with an information device, etc. as a control means for interpreting the protocol.
FIG. 1B shows the control elements in control unit 11 of conventional memory card 10.
Thus a conventional memory card has a main unit connection interface for connecting with the main unit of the information device, etc., and a memory interface for inputting and outputting data to and from the nonvolatile memory.
A conventional video game device such as a home video game device has the function of storing game data, etc. in an auxiliary memory. The memory card device is also used as an auxiliary memory of such video game device.
FIG. 2 shows an example of a conventional video game device that uses a memory card as an auxiliary memory. Main unit 2 of this conventional video game device 1 has a disk loading unit 3, which is accommodated in a roughly rectangular housing and in the center of which is mounted an optical disk, which is a recording medium on which video game application programs are stored, a reset switch 4 for resetting the game at will, a power switch 6, and, for example, two slots 7A and 7B.
Memory card 10, which is used as an auxiliary memory, is loaded in slots 7A and 7B, and for example, the results, etc. of a game played on the video game device 1 are sent from control means (CPU) 19 and are written into nonvolatile memory 16. Multiple operation devices (controllers) not shown can also be connected to slots 7A and 7B, allowing multiple users to play competitive games, etc. simultaneously.
One could further give the function of executing a game and other programs to a slave machine that is connected using the memory card slot of an entertainment system, which serves as the master machine. That is, it is thought that after at least part of a program such as a game will be downloaded from the master machine, the program itself will be executed, and if the program is a game, it will be given the function of allowing the growth, etc. of the characters in the game. Such a portable electronic device (slave machine) can be used without modification as a portable information terminal, and by making communication with other devices easier, its range of applications can be expanded, thereby leading to the stimulation of new demand.
Removed from the master machine, such a portable electronic device drives, using an AC adaptor, a battery, etc., a central processing unit (CPU) that performs image processing, audio processing, etc. In particular, a battery is used if the portable electronic device is used portably. With a portable electronic device in such a case, it is important how efficiently the limited battery is used.
Meanwhile, among portable electronic devices, with those that employ a system in which the speaker is driven from the CPU via a digital/analog converter (DAC), if a musical piece or sound effects are to be emitted, a frequency at least twice that of the frequency to be emitted is required, so it is considered difficult to emit high-quality sounds without a rather high operation clock.
However, as stated above, in order to emit high-quality sound with a portable electronic device in which a CPU and DAC are directly connected, the CPU operation clock must be made high, creating the problem of high power consumption.
This invention, which was devised with the above problems in mind, provides, for the problems to be solved, a method and device that can use the battery of a portable electronic device efficiently without lowering the quality of the music, sound effects, and other sound that is emitted.
According to a first aspect of the present invention, there is provided a method of reducing power consumption, wherein a speaker is driven under a CPU instruction, and when audio sound is to be output, an operation clock with a CPU is varied by a sound emission request. The operation clock can be changed to either a high-speed mode or a medium-speed mode by the sound emission request, and otherwise it is set to a low-speed mode.
According to a second aspect of the present invention, there is provided a portable electronic device comprising a speaker driven by a CPU via a digital/analog converter, wherein a sound emission request is input to a bus controller that is linked to said CPU; and a close variation means controlled in accordance with the input to said bus controller, and an operation clock is made variable.
According to a third aspect of the present invention, an entertainment system is provided, which includes an entertainment device that has a program execution function and a portable electronic device that is detachably mounted on said entertainment device and includes an interface for making an electrical connection to said entertainment device, and in which the portable electronic device comprising a speaker driven by a CPU via a digital/analog converter, wherein sound emission requests are input to a bus controller that is linked to said CPU; a clock variation means controlled in accordance with the input to said bus controller, and wherein an operation clock is made variable.